Peel kumara, and chop into bite-sized chunks. Place a sheet of baking paper which has been sprayed with olive oil into a baking dish. Add the kumara, and spray with olive oil. Roast until golden and tender. Cool.Place in a bowl with the mayonnaise, chopped sun-dried tomatoes and lemon juice. Mix well.Place spinach leaves on platter. Place kumara in the middle. Chop cherry tomatoes in half, and add to the kumara. Scatter with spring onions. Spoon over the mayonnaise. Scatter with parmesan and grind black pepper over the top.Serve at room temperature, or chilled.Serves 4.